Internal-combustion engine



E. W. ROBERTS INTERNAL COMBUSTION ENGINE Filed Got. 23 v 2 Sheets-meet 1 o 4 o Ia g1 49 Jug 2, 19 25.

E. W. ROBERTS INTERNAL COMBUSTION ENGINE Fi1ed 0ct. 23, 1920 2 Sheets-Sheet 2 it st cleric Z, 1925.

tantrum) w. nonn'a'rs, or chromium, onto,

mrnmvnncousus'rxon moms.

Application filed October 28, 1820.: Serial No. 418,868.

piston the inlet valve and the exhaust valve di erent points in the cycle. Fig. 9 shows a typical valve-timing diagram and indicates-the approximate points at which. the valves open and close during one revolution of the crankshaft and, incistlentally, during the completion of one cycle of o era-- cliom may concern:

known that l, EDMUND W. a citizen of the United States, Cincinnati, the county of Hamilton and wta'tnte of Uhio, have invented certain new and useful improvements in Internal'Comlgnstion Ne s which the following is Rosrn'rs, residing at n "pee tions. Like numbers of reference in icate l it in relates to certam new and. like parts throu hout the several figures. useful impw sweets in intemal-combustwn Referring to t e drawings, the numeral 1 gines oi the veciprocating type; and it has its objects the, complete scavenging of the cylinder, clearing it-entirel y of the prodnets of combustion, supercharging without the use of extraneous pumps or blowers and, incidentally thereto providing for the uni-v directional flow oi the out oing burned and the incoming fresh c large of pure mined sit and combustible, according to the system of fuel sup ly in use. As will he noteglnin the following specification, this system is generally ap licable to any l-com ustion engines,

designates the c linder surrounded by the Water-space 2 igs. 1 end 2), and in the cylinder reci roc'ates the piston 3 linked to t e cranksha t l by means of the connecting-- rod or -pitman 5, this arrangement follow in the well-known form of construction.

.lh'e base or crankcase 6 is made airtight, as is the usual practice with en ines of the two-stroke type. In the side or the base is a. cylindrical portion 7, having its axis parallel to the axis of the crankshaft. In this cylindrical portion is fitted a tubular valve 8 having an opening or port 9 ar rangedto re ister, at certain intervals in the rotation 0% the crankshaft, with the port 10 in the wall of the base. Valve 8 is driven at the same speed as the crankshaft 4, and

all

and all types of interns whether employed for automotive or for i ationary purposes, and whether operatin the ditto, the Diesel, the semi-Diesel,

= other the well known systems for plyingthe engine with,, combustible and in time therewith, by-means of the gears ll for the ignitiont'thereof. Thereand 11.. Alr enters valve 8 through pas not confinemyself to the particuas e 8".

' n the Wall of the or ports 12 which regl ing ports 13 in the w when the piston is-at t cor slll'llfitlfill hereinafter deml in the accompanymg es, nor to the exact mechanism 1llusiston 3 are openings ster with corres onrlall of the cylin er 1 he bottom 0 a f its stroke.

cntion in its simplest form, as These ports furnish communication for the app l on engine of the two-stroke cycle base wlth the by-pass or transfer passage 14, type, as shown in the accompanying drawand therethrough with the up or portion 5' w I of the cylinder by means of ports 13'. In the upper lnder and at its topmos passegeslfi and 1,5" in Fig. 1 and-l5" in Fig. 2, the passage of the gases (the r0ducts of combustion) from the cylinder liein controlled byv means of valves 16, 16 an 16'. The opening and 'closing of these valves is controlled, in the usual manner, by means of the cam 17, Fig. 1 or a similar cam not shown vfor Fig. '2, and the rocker I arms 18, 18" and 18",:in conjunction with the clbsing action of the springs 19, 19 and 19"; No particular method of driving the cam in Flg. 1 or of operating the rockerarm 18" in Fig. 2 is shown, as it is obvious that any one of the well ltnown methods of driving the camshaft may be employed for this purpose, and the pushrod in Fig.

t e cylinder portion of the cyl. t end are exhaust s valve. Figs. 4 to 8 in- .ertical sections through the eyl e .hodying my invention .elstive positions of the Elli llltl may be operated by means of the usual cam and gear train. A spark plug is indicated at 21. The general paths taken by the gases are indicated by arrows, dotted arrows signifying the exhaust and full-line arrows the fresh gases either air alone or mixed air and combustible In Fig. 3 is shown no form of crankcase inlet valve 8, which may be employed inone of the various means of furnishing communication between the base and the upper portion of the cylinder, such as a valve or valves in the headof the piston, tubular forms of transfer passage, such as may be formed of pipe or the like, valve-controlled transfer passages, and any one of the various methods of transfer control may be employed without departing from the purpose of this invention.

With the parts constructed and arranged as hcreinbefore described and as illust'ated in the accompanying drawings, the operation of the engine is substantially as. follows: With the parts in the position shown in Fig. l, the piston is at the upper ;de ad point having just completed .the 'compres sion stroke, combustionhas been started by means of an electric spark or other means, and the piston is about to start on its downward stroke, expanding the products of combustion. In the position-of Fig. 4, the tubular valv' 8 is about to close, but air is still entering the base due to the inertia of its mass. In Fig. 5, the crankshaft has 10- tated in the direction of the arrow through an angle of 120 beyond the position of Fig. 4 and the exhaust valve hasjust begun to open, the amount of such opening beingexaggerated in the figure for the sake of clearncss. Because 01" the comparatively high pressure within the cylinder, the same being about pounds above that of the at rnospherc, the exhaust gas, indicated by the dotted arrows, rushes rapidly "from the cylinder and the pressure therein quickly reaches that of the atmosphere, and the in ertia of the exhaust gas is such that the pressure within the cylinder tends to vfall below that of the atmosphere and produce a partial vacuum. In the position of the parts shown in this figure thevalyle 8 is closed, the new charge is trappedin the base and is being compressed by the down- Ward movement of the piston to a pressure 18 indicated by dotted-- of from 4 to 10 pounds per square inch above the pressure of the atmosphere. In Fig. 6 the crankshaft has advanced from the position of Fig. 4, and in the direction of the arrow, through an angle of J35.

-When the parts are in the position shown in Fig. 6, the exhaust valve 16 is fully open, and the top edge of the piston is'just beginning to uncover the ports 13, thereby opening communication, by means of the passage 14', with the base 6. Experience with this type of engine has shown that, during the movement of the piston from the position of Fig. 5 to that of Fig. t .,7j.bc pressure within the cylinder will fall to less than that in the base at this point, and-the pressure Within the base will force the new charge through the transfer passage H and the cylinder ports 13 into the cylinder above the piston. hen the parts are in the position shown in Fig. 7, the crankshaft has rotated further in the direction of the ar row and is now about from the position shown in Fig. 6 and about 190 from the position shown in Fig. 4. In Fig. 7, the exhaust valve 16 has begun to close, the new mixture,as indicated by the ful1-line ar-' rows, has practically filled the cylinder and the exhaust gas, indicated by the dotted arrows, has practically been driven from the an initial flow of new air or of mixed air and combustible, according to the, type of engine and its methodr'o'f fuel supply. It will be noted that this early opening of the valve 8 is appreciably in advance of the formation of any vacuum that would be produced by the upward movement of the piston 3, and that this early opening takes advantage of the inertia of the moving col.- umn of gas leaving the base and entering the cylinder, to increase the volume i fresh charge that may bc'drawn into the base orer and above that amount which would ordinarily be drawn into the base by the suction due to the piston alone. The. fresh charge enters the base by the following path, first from the atmosphere direct or from a carburetor or similar dev ce through the opening 8", thence into the central hollow portion of the valve 8 through suitable openings in the wall thereof and registering with opening 8', theme from the valve through port 9 in the valve and port 10 in the wall of the base. Fig. 8 shows the relative positions of the parts when the crankshaft has advanced in the direction of the 4 tion' of Fig. .4, or 30 past the lower dead' j Thereafter .the cycle, as

peated at each revolution ofthe crankshaft. In Fig. 9 is shown a valve diagram which arrow through an an le of from the position of Fig. 7, an 210? from the 'posi point. In the position shown in Fig. 8, the exhaust valve 16 has just closed, the ports 13- are partially closed and the valve 8 is more fully open, than in Fi '7." Immediately following the position o Fig. '8 and after a slightly further rotation of the crankshaft through an angle of about 15 from its position in Fig. 8, the. ports 13 are entirely closed by the piston and compression begins, followed shortly by ignition just in advance of the upper deadpoint position of Fig. 4, or by imection' of a charge of fuel as in the Diesel or the semi-Deisel types of engines.

cscribed, is reindicates approximately, the opening and the'closing positions of the various valves and ports and the sequence of these events. In the figure, the closing point of the tu- I bular valve 8 is indicated at IC, this point being about 15 after the piston has passed the upper dead point of Fig. 4. Thereafter follow in order the opening of the exhaust valve at X0, about 60. in advance of the lower dead point, the o' ening of the c'ylinder inlet port 13' at 45 in advance of the lower dead opening of the inlet valve 8 to 1( past the lower dead point, the closing of the exhaust'valve'lti at XC, about 30 past the lower dead pointand the inlet.

port 13 at PC, about 45. past the lower dead'point. s

By the herein described straight flow method of operatin charge is taken into the. cylinder, the cylinder' has been almost completely cleared of inert gases from previous explosions, thussecuring relatively greater space to receive the fresh charge. The volume of the fresh charge is thus increased and is further augmented through the surcharging of the -fresh charge into the cylinder from and at a higher'pressure than in the crank case,

while the pressure and volume in the crank case has, already been augmented due to the sl'ircharging effect attained in introducing the fuel into the crank case. The explosive energy and mean ctl'cctivc pressure is ,therefore materially reator for a given cylinder displacement than with en- The increase in mean efi'ective .pressure results in increased power per unit volume, and also results in further fuel economy through less loss of heat per unit volume by exposure to and 0, approximately point, the 0, about a two-cycle 'engine several important a vantages 1n perform-- ance are attained. Before a fresh lfuel conduction through the cylinder walls.

further increased etliciency results through less frictional loss per unit volume, since the frictional loss is a constant invproportion to the size of the parts and irrespective of the load. Also due to the straight-flow,

the respective fuel ports may be of relatively greater area, and hence greater engine speeds are permissible up to practically double the speed heretofore attainable. The

straight flow also enables elfective compression to commence at an earlier stage than usual so that the effective length of the cylinder is increased b approximately ten per cent over two cyc e engines heretofore in use, which further adds to the mean effective pressure and hence to the'efliciency and fuel economy. I- am therefore enabled to develop an ual amount of power by employing a sma ler en inc, and one of ma terially less weight t an heretofore required,

The most advantageous timing of the valves for any one design of-enpinemay be determined by .experimenfion' y and the valve ap s e'varied from one desig i BI to ano V 7 the cycle whichis-employed, and,the conditions of the service for which the "engine isto be used. Therefore Ido'not confine to meet the conditions'bf speed myself to the exact timing shown in the figures, but reserve the right to depart there-f from according to the re ulrements of each individual case, as it is o vioiis that a considerable variation in the points of iopening the valves and the ports may. out departing from-the basic and of closin be made with principlesof my invention.

What I claim is:

A two.- cycle internal combustion engine J com rising a cylinder, a piston, an enclosed cran pitserving as a precompression chamher, an exhaust, valve located at thehead end of said cylinder, a piston controlledport leadin from said crankit to the interior of sai cylinder, and a va ve for theradmission .of a fresh charge tb the, crank pit,

said exhaust valve 1ston controlled port ing timed in the foland admission valve lowing order, the exhaust valve to open, the

piston controlled port to open, the admission valve to open, the exhaust valve to close,'the piston controlled port to close, the;

admission valve toclosc, whereby the crank pit 1s sin-charged from its exterior and the cylinder is subsequently surcharged from j signature.

EDMUND W. ROBERTS. 

